Isomerization of paraffins



Patented Apr. 13, 1943 lsonamznrrox or ranarrms Vladimir N. Ipatiel! and111., assignors to Unive Herman Pines, Ghicago, rsal Oil Products COM-.-

- pany, Chicago, 111., a corporation ot Delaware No Drawing. ApplicationJanuary 12,1940, Serial No. 313,527

Claims. (circa-essay This invention relates to the treatment ofparafiins to produce more highly branched hydrocarbons and particularlyto the treatment of butane of normal or straight chain structure.

More specifically the invention is concerned with a process wherebynormal butane is converted into isobutane, the process involving the useof special catalysts and particular conditions of operation which favorisomerization so that the iso-compound is produced in relatively highyield.

Since the invention ic concerned principally with the two 4-carbon atomparaflln hydrocarbons and their transformation, one into the other, thefollowing table is introduced to indicate the structure and theprincipal physical characteristics of these two compounds:

Properties of butanes Butanes are produced in considerable quantities inthe oil refining industry. They occur in substantial amounts in naturalgases (in which the normal compound usually predominates), in refinerygases which are evolved from crude petroleum storage tanks, and in theprimary distillation of crudes, and they are also present inconsiderable percentages in the gases produced incidental to crackingheavy petroleum fractions for the production of gasoline. In the case ofcracked gas mixtures therelative proportions of isoand normal-butanesvary, but the ratio of the isoto the normal-compound is as a ruleconsiderably higher than in natural gas.

Butanes may be considered as more or less marginal compounds in respectto their desirability in ordinary gasoline, that is, a certainpercentage of them is essential for suflicient vapor pressure to insureease in starting, while an excess tends to produce vapor look. For thesereasons the total percentage of 4-carbon atom hydrocarbons is commonly.adjusted in conjunction with the boiling range and vapor pressure of theother gasoline components to produce a gasoline oi! desirable startingcharacteristics according to seasonal demands.

The butanes at the present time bear a further important relationship tooil refining in that their excess production is belng utilized as asource of gasoline either by ordinary thermal cracking or by specialcatalytic dehydrogenation processes followed by polymerization in whichcatalysts may or may not be used. Investigations have shown thatisobutane is considerably more amenable to cracking and dehydrogenation,both with and without catalysts, than the normal compound. Consideringthe corresponding monoolefins, the normal butenes are considerably moredifficult to polymerize, either thermally or catalytically, thanisobutene, and it is found that also the octenes representing the dimersof isobutene are of a higher antiknock value than those from n-buteneswhich holdsalso for the octanes produced by hydrogenation; It is,therefore, of considerable importance at the present time to convert asmuch as possible of the normal butane production into isobutane, and thepresent invention is especially concerned with a process foraccomplishing. this object.

In one specific embodiment the present invention comprises a process forproducing isobutane from normal butane which comprises contacting saidnormal butane with a composite of substantially anhydrous chlorides ofaluminum and copper and a porous adsorbent in the presence of small butdefinite quantities of hydrogen halide and under isomerizing conditionsof temperature and pressure.

We have determined by the use of the class of catalysts mentioned, andparticularly by the concurrent use of considerable 'superatmosphericpressure, normal butane may be converted into approximately 30-60% ofisobutane per pass. Practical yields ofisobutane are obtainable attemperatures within the approximate range of C. under pressures of theorder of I to 200 atmospheres and preferably of 10 to 200 atmospheres attemperatures of C. and higher. Besides depressing the volatilization ofaluminum chloride from such catalysts, pressure tends also to diminishnumerous undesirable side reactions which would result in the formationof hydrogen and of low molecular weight hydrocarbons. so that thereaction proceeds more or less in one direction until an equilibrium isestablished.

There are several alternative catalysts consisting of aluminum chlorideand copper chloride on inert carrying materials which may be employed inefiecting the lsomerization of normal butane to isobutane; and whilethey may be used more or less interchangeably, some are more effectivethan others, and accordingly it is not intended to infer that they aredefinitely equivalent. Extensive experiments have indicated that bestresults are obtained when a minor percentage of a hydrogen halide,usually in the approximate range of 0.540% by volume of the butane, is

' present in the reactions and the necessary amount of hydrogen halidemay be introduced directly or produced in situ by small amounts of wateror steam, which cause a certain amount of hydrolysis of thesubstantially anhydrous chlorides.

One of the essential features of the present in- 'vention is the-,use ofactive aluminum chloride diluted by copper chloride in conjunction withporous granular supports. This use of supports facilitates vapor phaseoperations at temperatures above the sublimation point of aluminumchloride and apparently in some instances seems to lessen the tendencyto the formation of sludges consisting of complex addition compounds sothat the life of the catalyst extended materially.

When granular aluminum chloride is employed alone in hydrocarbonreactions, it soon tends to agglomerate on account of the formation ofadhesive sludge-like'materials so that violent agitation is necessary tomaintain contact of the catalyst with the reacting hydrocarbons. Amongsupporting materials which we have now shown to have practical value ascarriers may be mentioned activated carbon, pumice, various types offullers earths and clays, particularly those of the montmorillonite orbentonite types, either raw or acid treated, diatomaceous and infusorialearths, kieselguhr, silica-alumina composites, unglazed porcelain,flrebrick, and, in general, refractory porous substances which havesubstantially no reactivity with the anhydrous chlorides. It happensfrequently that one type of support is better than others, dependingupon the ratios of chlorides and support found experimentally to be thebest for the furtherance of a particular isomerizing reaction so that itis not to be inferred that the supports can at all times be usedinterchangeably.

A property of anhydrous aluminum chloride which must be taken intoaccount is its tendency to sublime at a temperature of approximately 180C., so that if it is employed at temperatures above this pointit mustordinarily be injected or subiimed into the reaction zone. I.

In the process of the present invention in' which the mixture ofaluminum chloride and cupric chloride employed is strongly adsorbed bygranular material, the enumerated disadvantages of unsupported aluminumchloride are overcome to a large extent since the tendency of aluminumchloride to volatilize is particularly counteracted by the adsorbentaction of the supports employed, and these supports further act toadsorb-and retain some of the viscous addition compounds and prevent thecomposite catalyst granules from adhering to form large agglomerates.

'A general method of preparation of the types oxide deposited upon thecarrier. The carrier and supported cupric oxide may then be driedpreferably in a stream of an inert gas as nitrogen at approximately 200C. A slow stream of hydrogen chloride is then passed over the driedgranula material as its temperature is increased slowly fromapproximately 200 to 400 C. during which the material changes color fromdark blue to dark brown, characteristic of anhydrous cupric chloride.

The resultant .granular composite of carrier 7 and copper chloride isthen mixed with the deof granules whose use in butane isomerizationcharacterizes the present invention consists in precipitating cupricoxide upon acarrier, for example flrebrick, converting the cupric oxideto copper chloride and compositing the'resultant V granular materialwith aluminum chloride. This procedure may be carried out byimpregnating the carrier with an aqueous solution of cupric chloride,then adding a basic precipitant as ammonium hydroxide to form ilnelydivided cupric oxide or copper hydroxide, after which the aqueoussolution is evaporated to leave the "cupric 76 sired quantity ofanhydrous aluminum chloride and heated in a pressure vessel atapproximately 250 C. preferably in the presence of hydrogen chloride andunder approximately 25 atmospheres pressure of hydrogen or of anotherinert gas. After treating the granules of copper chloride and carrierwith aluminum chloride, the composite obtained appears dry and thealuminum chloride has apparently disappeared although its presence in,the pores and on the surface of the composite is evident by the violentreaction of the granules with water and their catalytic activity inorganic reactions. This procedure is typical of the preparation of anynumber of similar catalytic materials using different proportions ofmetal chlorides on the supportsherein mentioned.

The addition of copper chloride to aluminum chloride used for preparinga supported isomerization' catalyst increases theisomerizing activityand life over that obtainable with similar catalytic material consistingof aluminum chloride only deposited upon substantially inert supports.In the presence of the supported aluminum chloride-copper chloridecatalyst there is also relatively small formation of propane and pentanefrom butane by side reactions.

Owing to the adsorptive properties of the supports, catalysts of theabove character may be employed in isomerizing normal butane withsubstantially no tendency for the original particles to run together dueto the formation of intermediate sludge-like products, so that muchlarger quantities of material may be treated before the catalyst haslost its activity. Another advantage resides in the fact that theadsorbed halides will remain in place without volatilization presentspecification is intended to include any' type of prepared carbon orcarbonaceous mate-' rial which is more or less granular and possessed ofgood porosity and structural strength and which has been prepared bygeneral steps involving the leaching of adsorbed material from granularresidual carbonaceous materials such as wood char and various varietiesof coke by mineral acids and by the controlled heating, preferably undervacuum, to expel adsorbed liquids and gases. It is recognized thatvarious forms of active granular chars will vary considerably inadsorptive capacity and, therefore, the properties of catalysts preparedwhen using them in accordance with the present invention will vary bothin respect to the amount of aluminum and copper chlorides which they areable to adsorb and in respect to the periods of service in which theyare able to maintain a practical activity in different organicreactions.

The present butane isomerization process may be operated under batch orcontinuous conditions and either in liquid, mixed, or vapor-phase as maybe desirable or expedient in view of the V tion mixture also tends todecrease sludge formation and prolong the life of the catalyst compositeemployed in isomerization reactions.

In another type of operation which accelerates the rate ofisomeri'zation, the hydrocarbon mixture may be kept at its boiling pointby moderate heating under reflux conditions with the granular catalystmaintained in suspension by the ebulition, while the hydrogen halide isadded .in a slow stream. In this type of operation any sure of 25atmospheres.

while the temperature was increased from 200 to 400 C. over a period ofhours during which a dark brown color characteristic of anhydrous cupricchloride developed in the granular composite. The flrebrick containingcupric chloride was, next mixed with 50 parts by weight of aluminumchloride and heated in an autoclave atv 250 C. in the presence of 10parts by weight of hydrogen chloride and under a hydrogen presnfter thistreatment for two hours a granular composite was obtained containing 30parts by weight of aluminum chloride, 3 parts by weight of cupricchloride, and 70 parts by weight of flrebrick. A

Normal butane containing 4% by volume of hydrogen chloride was passedthrough a tube containing 4'7 parts by weight (75 volumes) of the abovedescribed granular composite at 200 C. under a pressure of 45atmospheres.

20 butane which had been saturated previously with desiredsuperatmospheric pressure may be emplayed to permit the use of anydesired temperature. In the case of a supported aluminum chloride-copperchloridecomposite, the necessary amount of hydrogen chloride may begenerated by adding a small amount of water or steam which causeshydrolysis.

Vapor phase isomerization operations may be conducted by passing vaporsof hydrocarbons 7 mixed with a small amount of hydrogen chloride overcatalyst composites in the form of granules or pellets which arecontained in treating chambers or reactors. Addition of hydrogen to suchreaction mixtures has a beneficial effect similar to that observedduring its use in batch operatlons.

' While the catalyst and process of this invention are particularlyuseful in isomerizing normal butane into isobutane, they may be usedalso for isomerizing normally liquid paraflins into more branchedisomeric parafilns under conditions of temperature, pressure. and timerfound to be optimum for the isomerization of the hydrocarbons orhydrocarbon mixtures undergoing treatment.

The following example is introduced as char acteristic of the practicaloperation of the present process although not with the intention oflimiting the scope of the invention in exact correspondence with thenumerical data since some latitude is possible in the proportions ofadsorbent, aluminum chloride, and copper chloride; and temperatures andpressures may also be varied within the limits already specified. Thesevariations may be-considerable in the case of gas mixtures in which thenormal butane content varies over relatively wide ranges.

Example A solution containing 3 parts by weight of copper chloride in300 parts by weight of water was added to 90 parts by weight of 6-10mesh crushed flrebrick and then ammonium hydroxide was then passed overthe dried gramlar composite hydrogen under 45 atmospheres pressure wascharged at the rate of 1.1- volumes per hour per volume of reactor spacecontaining the granular composite catalyst. It was found that 4,850volumes of liquid isobutane and 610 volumes of pentane were formed from14,200 volumes of normal butane in the presence of the volumes ofgranular composite catalyst before the isomerization decreased to 15%per pass. During the run, the average molar composition of the exitgases per pass was 4.7% propane, 34.2% isobutane, 56.8% normal butane,and 4.3% pentanes. A similar catalyst but without copper chloride undersimilar conditions produced 3.570 volumes of liquid isobutane and 440volumes of pentanes from 11,000 volumes of normal butane before thepercentage isomerization decreased to 15% per pass.

The character of the present invention and its novelty and utility inproducing isobutane from normal butane in the presence of supported aluminum chloride-copper chloride composites can be seen from the precedingspecification and nu merical data presented although neither section isintended to unduly limit its generally broad scope.

We claim as our invention:

1. A process for the isomerization o paraflin hydrocarbons to producetherefrom substantial yields of compounds more highly branched than thematerials subjected to treatment which c mprises subjecting saidhydrocarbons mixed with a hydrogen halide to contact with aranularcomposite of substantially anhydrous chlorides of aluminum andcopper and a relatively inert adsorbent under isomerizing conditions oftemperature and pressure.

2. A process for the isomerization of normally liquid paraiflnhydrocarbons to produce therefrom substantial yields of compounds morehighly branched than the materials subjected to treatment whichcomprises subjecting said hydrocarbons mixed with a hydrogen halide tocontact with a granular composite of substantially anhydrous chloridesof aluminum and copper and a relatively inert adsorbent underisomerizing conditions oi temperature and pressure.

3. A process for the isomerization of normal butane to produce therefromsubstantial yields of isobutane which comprises subjecting said normalbutane mixed with a hydrogen halide to contact with a granular compositeof substantially anhydrous chlorides of aluminum relatively inertadsorbent.

4. A process for and copper and a n butane to produce therefromsubstantial yields of The normal the isomerization of normal isobutanewhich comprises subjecting said normal butane mixed with a hydrogenhalide to contact with a granular composite of substantially anhydrouschlorides of aluminum and copper and a relatively inert siliceousadsorbent.

5. A process for the isomerization of normal butane to produce therefromsubstantial yields of isobutane which comprises subjecting said normalbutane mixed with a hydrogen halide to contact at a temperature withinthe approximate range of 50-350 C. with a granular composite ofsubstantially anhydrous chlorides of aluminum and copper and arelatively inert adsorbent.

6. A process for the isomerization of normal butane to produce therefromsubstantial yields of isobutane which comprises subjecting said normalbutane mixed with a hydrogen halide to contact at a temperature withinthe approximate range of 50-350 C. with a granular composite ofsubstantially anhydrous chlorides of aluminum and copper and arelatively inert siliceous adsorbent.

7. A process for the isomerization of normal butane to produce therefromsubstantial yields of isobutane which comprises subjecting said normalbutane mixed with a hydrogen halide to contact at a temperature withinthe approximate range of 50-350" C. under a pressure of a substantiallyinert gas from substantially atmospheric to approximately 200atmospheres with a granular composite comprising essentially anhydrouschlorides of aluminum and copper and a relatively inert adsorbent.

8. A process for the isomerization of normal butane to produce therefromsubstantial yields of isobutane which comprises subjecting said normalbutane mixed with a hydrogen halide to contact at a temperature withinthe approximate range of 50350 C. under a pressure of an inert gas fromsubstantially atmospheric to approximately 200 atmospheres with agranular composite comprising essentially anhydrous chlorides ofaluminum and copper and a relatively inert siliceous adsorbent.

9. A process for the isomerization of normal butane to produce therefromsubstantial yields of isobutane which comprises subjecting said normalbutane mixed with a hydrogen halide to contact at a temperature withinthe approximate range of 50-350 C. under a pressure of hydrogen fromsubstantially atmospheric to approximately 200 atmospheres with agranular composite comprisins essentially anhydrous chlorides ofaluminum and copper and a relatively inert adsorbent.

10. A process for the isomerization of normal butane to producetherefrom substantial yields of isobutane which comprises subjectingsaid normal butane mixed with a hydrogen halide to contact at atemperature within the approximate range of 50-350 C. under a pressureof hydrogen from substantially atmospheric to approximately 200atmospheres with a granular composite comprising essentially anhydrouschlorides of aluminum and copper and a relatively inert siliceousadsorbent.

11. A process for the isomerization of normal butane to producetherefrom substantial yields of isobutane which comprises subjectingsaid normal butane mixed with a hydrogen halide to contact at atemperature within the approximate range of 50-350 C. under a pressureof hydrogen from substantially atmospheric to approximately 200atmospheres with a granular composite consisting of activated carbon andsubstantially anhydrous chlorides of aluminum and copper.

12. A process for the isomerization of normal butane to producetherefrom substantial yields of isobutane which comprises subjectingsaid normal butane mixed with a hydrogen halide to contact at atemperature within the approximate range of 50-350 C. under a pressureof hydrogen from substantially atmospheric to approximately 200atmospheres with a granular composite of crushed firebrick andsubstantially anhydrous chlorides of aluminum and copper.

13. A process for the isomerization of normal butane to producetherefrom substantial yields of isobutane which comprises subjectingsaid normal butane mixed with a hydrogen halide to contact at atemperature within the approximate range of 50-350" C. under a pressureof hydrogen from substantially atmospheric to approximately 200atmospheres with a granular composite of diatomaceous earth andsubstantially anhydrous chlorides of aluminum and copper.

14. A process for isomerizing parafiln hydrocarbons which comprisescontacting the parafiins under isomerizing conditions with a solidcatalyst comprising aluminum chloride and copper chlo- 15. A process forproducing isobutane which comprises contacting normal butane underisomerizing conditions with a solid catalyst comprising aluminumchloride and copper chloride.

VLADIMIR N. IPATIEFF. HERMAN PINES.

